Homeland Security Secretary Jeh Johnson, New York City Mayor Bill de Blasio and others and looked back on 9/11 at an event commemorating the federal government's return to One World Trade Center Friday.

"As Americans, it is important that each year, we honor and remember those who lost their lives that day, and that we honor the heroes on that day, and recall how 911 changed our nation and our world," Johnson said.

The meeting comes two days before the 15th anniversary of the deadliest terror attack on U.S. soil.

"It is something that now is a symbol to people around the world of resilience, fortitude," de Blasio said. "They come here to recognize the ultimate victory of the people of this country over the terrorists"

One of the speakers was Michael Byrne, a member of the FDNY on 9/11 and now a deputy regional administrator of FEMA.

"No matter how much it hurts, when you are in the military or public service you have no choice but move on," Byrne said. "We had a job to do, and we did it. Today, we share that call to service, and we feel a renewed commitment in this beautiful building to continue the mission for which our fallen friends gave their all."

Several federal offices were located in the two towers of the World Trade Center prior to the attacks and have since returned to the new structure.

"It was not an accident that this is 1,776 feet high," Lieutenant Governor Kathy Hochul said. "That's a reminder of the birth of our nation, but also the rebirth of this site. That is something that is always going to be a part of us, to realize the very existence of this building says that we're Americans, we're New Yorkers, and we always come back."

Customs and Border Protection, the Federal Office of Emergency Management and the General Services Administration now occupy floors at One World Trade.

The move was not without controversy, however, as some employees sued to try to prevent the move out of fear of being targeted by terrorists.